Average global air and ocean temperatures are rising, leading to the melting of snow and ice
and rising global mean sea level. Ocean acidification results from higher CO2 concentrations.
With unabated greenhouse gas emissions, climate change could lead to an increasing risk of
irreversible shifts in the climate system with potentially serious consequences. Temperature
rises of more than 1.5–2 °C above pre-industrial levels are likely to cause major societal and
environmental disruptions in many regions. The atmospheric CO2 concentration needs to be
stabilised at 350–400 parts per million (ppm) in order to have a 50 % chance of limiting global
mean temperature increase to 2 °C above pre-industrial levels (according to the IPCC in 2007,
and confirmed by later scientific insights).

Published by

EEA (European Environment Agency)

Published: 28 Nov 2010

Content

Summary

What are the current and projected future greenhouse gas concentrations?

In the year 2009, the atmospheric CO2
concentration was about 387 ppm, which is 38 % above the pre-industrial
level of 278 ppm. The concentration of the six greenhouse gases (1) covered by the Kyoto Protocol reached 438 ppm CO2-equivalent
in 2008, an increase of 160 ppm from the pre-industrial level. Under
the emissions scenarios of the Intergovernmental Panel on Climate Change
(IPCC), the overall concentration of the six 'Kyoto gases' is projected
to increase to 638–1 360 ppm CO2-equivalent by 2100.

What are the main changes in the climate system?

The
global mean temperature in 2009 was between 0.7 and 0.8 °C higher than
in pre-industrial times and the decade 2000–2009 was the warmest on
record. Europe has warmed more than the global average. The annual
average temperature for the European land area was 1.3 °C above the
1850–1899 average. Without global emission reductions, the IPCC expects
global temperatures to increase further by 1.8–4.0 °C above 1980–1999
levels by 2100. Global temperature increase would exceed 2 °C above
industrial times – the limit agreed by the EU — between 2040 and 2060 in
all IPCC scenarios. The rise in temperatures has had, and will continue
to have, serious impacts on various parts of the climate system. Some
examples are:

The extent of Arctic summer sea ice has declined by about 10 % per
decade since 1979. The extent of the minimum ice cover in September 2007
was half the size of the normal minimum extent in the 1950s; the third
lowest minimum occurred in September 2010. Summer ice is also getting
thinner and younger.

Observed global mean sea-level rise has accelerated over the past 15
years. From 2002 to 2009, the contributions of the Greenland and West
Antarctic ice sheets to sea-level rise increased. In 2007, the IPCC
projected a sea level rise of 0.18 to 0.59 m above the 1990 level by
2100. Recent projections show a maximum increase of about 1.0 m by 2100,
while higher values up to 2.0 m cannot be excluded.

Glaciers in the Alps lost about two-thirds of their volume between 1850
and 2009. The glacierised area in the Alps is projected to decrease to
about one-third of the present area with a further rise in Alpine summer
temperature of 2 °C.

Acidification is occurring in all ocean surface waters as a result of increased atmospheric CO2
concentrations. Coral reefs worldwide, which are centres of
biodiversity and important as fish breeding grounds, are threatened by
both ocean acidification and increasing temperatures. By 2100 the pH
value could drop to 7.8, an increase in ocean acidity by 150 % compared
to the pre-industrial pH of 8.2. The acidity of the ocean would be
higher than at any time in the past 20 million years.

What are the global risks of climate change?

Land and ocean sinks have taken up more than half of global CO2 emissions since 1800. But these natural sinks are vulnerable. They are highly likely to take up less CO2
in the future. Moreover, poor nations and communities, ecosystem
services and biodiversity are particularly at risk. A temperature rise
of more than 1.5–2 °C above pre-industrial levels could cause
disruptions in many regions. Unabated greenhouse gas emissions increase
the risk of large-scale irreversible shifts in the climate system with
potentially serious consequences for society and ecosystems. Recent
research suggests that several key components of the climate system
could undergo irreversible change at significantly lower levels of
global temperature increase than previously assessed. The most important
'tipping elements' for Europe are the Greenland ice sheet, Alpine
glaciers and Arctic sea ice.

What are the targets to limit global climate change?

To
limit impacts and guide policy development, the Copenhagen Accord of
December 2009 recognised a long-term climate limit of 2 °C global mean
temperature increase, without specifying the base year. The Accord also
mentions the need for a review in 2015 to consider a possible goal of
limiting temperature rise to 1.5 °C on the basis of new scientific
insights. According to the IPCC (2007), confirmed by later scientific
insights, to have a 50 % chance of limiting the global mean temperature
increase to 2 °C above pre-industrial levels, the atmospheric greenhouse
gas concentration needs to be stabilised at about 445 to 490 ppm CO2-equivalent (or about 350 to 400 ppm CO2). To achieve this, global emissions should peak at the latest in 2015–2020 and decline to 50–80 % below 2000 levels by 2050.

(1) Carbon dioxide (CO2), methane (CH4), nitrous oxide which is also known as laughing gas (N2O), hydrofluorocarbons (HFC), perfluorocarbons (PFC) and sulphur hexafluoride (SF6). Greenhouse gases are often measured in CO2-equivalent in order to allow for comparisons of their potential to contribute to global warming.